Rayon bleaching and scouring treatment



Patented Apr. 17, 1945 UNITED STATES PATENT OFFICE RAYON BLEACHING ANDSCOURING TREATMENT No Drawing.

Application April 27, 1940,

Serial No. 332,012

8 Claims.

This invention relates to an improved process for the treatment offabrics of vegetable origin whereby scouring,.desizing and bleachingoperations may be effected simultaneously. The process of the inventionis of particular advantage in the treatment of unfinished fabrics of arayon, or containing a large proportion of rayon fibers, such as spun orfilament rayon.

Greige cloth and similar newly woven fabrics have a very limited use.For most purposes, they must be subjected to further treatment to placethem in salable form because, first, the natural color bodies occurringin the vegetable fibers detract from the appearance of the fabric,second, they contain varying amounts of motes (i. e., nonfibrousparticles such as cottonseed fragments) that adhere to the fibersthroughout the spinning and weaving processes, and third, the presenceof natural waxes and pectins and of sizings, principally starchy (whichare applied to the warp threads during weaving) makes the fabricwaterrepellent and thus tends to interfere with bleaching or dyeing.Removal of these various impurities from the fabrics so as to renderthem white and absorbent frequently involves a long and extensive seriesof treatments, and in general the more delicate and finer fabrics (whichwill not withstand the action of strong hot alkalies) require the longerand more complex treatments. Thus, certain cloths, including cotton andrayon mixtures used extensively in corset cloth and draperies, spunrayon and spun rayon mixtures, yarn dyed fabrics such as marquisettewith colored dots and shirting with colored stripes, velveteen, tafietaand corduroy, are usually subjected to a mild, long and complextreatment in such equipment as Rodney-Hunt kettles, becks, jigs and thelike. Such complex treatments are exemplified by that in a Rodney-Huntkettle which, for a heavy cloth, involves the following series ofoperations: desizing, usually by malting; a hot water wash to removemalt and such starch as has been solubilized; scouring. usually withsoap and weak alkali; a second water wash; bleaching, usually withsodium hypochlorite; a third water wash; an anti-chlor wash, a fourthwater wash.

In the process of the present invention the above-enumerated series ofoperations is simplified and shortened to the end that substantialsavings in time, labor, equipment and reagents are realized.Furthermore, the results attained with respect to desizing, scouring andbleaching are not only attained concurrently but are superior to thoseachieved by the more complicated methods of the art. By the use of theprocess of this invention a whiter cloth which is more absorbent, has asofter hand and lower starch content, and which has suffered lessdeterioration than in heretofore customary practice is obtained.

In accordance with this invention impurities and substances whosepresence is undesirable, such as natural color bodies and sizings, maybe satisfactorily and simultaneously removed from unfinished rayonfabrics by subjecting the fabric to the action of an alkaline aqueoussolution having dissolved therein hydrogen peroxide and a syntheticorganic detergent salt which is watersoluble, free of fatty acid salt orester substituents, active in the presence of the alkali and resistantto decomposition and oxidation by the hydrogen peroxide present. Such anoperation, which simultaneously desizes, scours and bleaches, may becarried out in any suitable apparatus, such as for example a Rodney-Huntkettle.

The alkalinity required by the process of the invention may be producedby any suitable alkali or alkaline buffer substance capable of producingand maintaining a moderate hydroxyl ion concentration in the treatingsolution. Best results are obtained in solutions in which the pH valueis not greater than about 11 to 12. One particularly effective and cheapreagent suitable for this purpose is sodium silicate. A concentration ofsodium silicate approximating 5 grams per liter produces a treatingsolution having a pH of 9.4, and a concentration of silicateapproximating 10 grams per liter produces a treating solution having apH of 10.9. Silicate concentrations of this order of magnitude areappropriate for the process of the invention, the exact quantity usedbeing dependent on the type of material treated and amount of impuritiespresent.

The concentration of hydrogen peroxide will also be governed by theproperties of the unfinished fabric being treated and. the difficulty ofproducing the desired whiteness in that particular fabric. In general wehave found that satisfactory results are obtained by using quantities ofvolume H202 solution appropriate to give aqueous solutions containingbetween about 1 gram per liter and 6 grams per liter of 100 volumeperoxide. The peroxide solution known as 100 volume peroxide is areadily available commercial product in the form of an aqueous solutionand averages about 27.4% H202 by weight. The stated range of 1 to 6grams per liter is therefore equivalent to a range of about 0.275 toabout 1.654 grams per liter pure H202.

The ynthetic detergent to be employed must exert its detergent actionand be active in the presence of the alkali concentrations in thetreating solutions and must be resistant to decomposition and oxidationby the hydrogen peroxide. The detergents which we prefer are sulfated orsulfonated high molecular weight organic compounds which are watersoluble salts free of fatty acid salt or ester substituents which inwarm or hot alkaline solutions would undergo hydrolysis with theconsequent production of ordinary alkali metal soaps. As examples ofsuch high molecularweight organic sulfates and sulfonates may bementioned sodium lauryl sulfate, sodium oleyl sulfate, sodium stearylsulfate, sodium lauryl sulfonate, sodium decyl benzene sulfonate, sodiumdodecyl benzene sulfonate, or salt of other sulfonated alkylatedbenzene, sodium hexadecyl sulfonate or mixtures of this and similarsulfonated aliphatic hydrocarbons, and sodium-2 methyl pentane-4sulfate. It is to be understood that compounds other than those justmentioned, or mixtures thereof, are suitable provided they are higherorganic sulfates or sulfonates free of fatty acid salt or estersubstituents, and provided they have the other above-describedproperties. We have found that sodium lauryl sulfate and sodium oleylsulfate give particularly good results. It will be understood that bythe expression free of fatty acid salt or ester substituents used herein1 in identifying our detergent, we intend to indicate that the detergentcontains no free or combined carboxyl group. The concentration of thedetergent is not particularly critical except that enough should beemployed to emulsify the impurities present in the textile. Hence theproportion will depend upon the particular detergent, the amount ofimpurities to be removed and the speed with which removal is to beaccomplished. In most cases concentrations approximating /2 gram perliter to 1 gram per liter will be satisfactory.

Most effective operation of the present process is attained atrelatively high solution temperature, 80 C. being a particularlyadvantageous temperature at which to treat most fabrics. Any elevatedtemperature, substantially above room temperature and below the boilingpoint of the solution, may be used.

The time of treatment will vary according to the fabric being treated,the quantity of impurities present and the difficulty of their removal.In general we have found that a reaction time ranging from one to twohours is satisfactory to produce the desired results, although in someinstances a period of /2 hour will be found sufficient.

The process of the invention will be illustrated by the followingexamples of small scale operation. The only important difference betweensuch operation and large scale commercial runs which we have noted isthat the large scale operations sometimes require treating solutionshaving a slightly higher H202 concentration. In each of the followingillustrative examples /8 yard of cloth was placed in a pint jar with 125c. c. of treating solution. These jar were agitated while immersed inwater maintained at a temperature approximating 80 C.

Example I Spun rayon was treated in an aqueous solution containing 4.33g. p. l. 100 volume H202, g. p. 1. sodium silicate which caused thesolution to have a pH value approximating 9.4, and /2 g. p. 1. sodiumlauryl sulfate. The treatment was continued for /2 hour at the end ofwhich time the cloth had attained a brightness value of 74.4 as measuredon a G. E. refiectometer, had a good absorbency and soft hand, and hadbeen partially freed of its original high starch content. In a similarrun employing the same reagents and conditions except for thesubstitution of 1 g. p. l. of soap for the synthetic organic detergent,the brightness attained was 72.6, the absorbency was poor, and thestarch removal was negligible.

Example II Rayon taffeta was treated in an aqueous solution containing1.08 g. p. 1. volume H202, 10 g. p. 1. sodium silicate which caused thesolution to have a pH value approximating 10.9, and /2 g. p. 1. sodiumlauryl sulfate. The treatment was continued for 2 hours at the end ofwhich time the cloth had a brightness value of 75.6, good absorbency andsoft hand, and a very low starch content.

Tensile strength measurements made on other samples of cloth treated inthe manner and under the conditions described in these examples indicatethat the cloth is not materially weakened as a result of such atreatment, either with respect to the warp strength or the fillerstrength.

We claim:

1. In the treatment of rayon containing colo-r bodies and starchysubstances, the improvement which comprises simultaneously scouring andbleaching the rayon by subjecting it in a single immersion treatment tothe action of an alkaline aqueous solution having dissolved thereinhydrogen peroxide in a concentration within the range of about 0.275 toabout 1.65 grams per liter and a synthetic organic water-solubledetergent salt having no free nor combined carboxyl group, whichdetergent salt is active in the presence of the alkali and is resistantto decomposition and oxidation by the hydrogen peroxide.

2. In the treatment of rayon containing color bodies and starchysubstances, the improvement which comprises simultaneously scouring andbleaching the rayon by subjecting it in a single immersion treatment tothe action of an alkaline aqueous solution maintained at an elevated.temperature and having dissolved therein hydrogen peroxide in aconcentration within the range of about 0.275 to about 1.65 grams perliter and a synthetic organic water-soluble detergent salt having nofree nor combined carboxyl group, which detergentsalt is active in thepresence of the alkali and is resistant to decomposition and oxidationby the hydrogen peroxide.

3. In the treatment of rayon containing color bodies and starchysubstances, the improvement which comprises simultaneously scouring andbleaching the rayon by subjecting it in a single immersion treatment tothe action of an alkaline aqueous solution having dissolved thereinhydrogen peroxide in a concentration within the range of about 0.275 toabout 1.65 grams per liter and a synthetic organic Water-solubledetergent salt having no free nor combined carboxyl group, whichdetergent salt is active in the presence of the alkali and is resistantto decomposition and oxidation by the hydrogen peroxide, said detergentbeing selected from the group of high molecular weight organic compoundsconsisting of aliphatic alcohol sulfates, aliphatic sulfonates andalkylated aromatic sulfonates.

4. In the treatment of rayon containing color 9% ill timers $1 H359.

bodies and starchy substances, the improvement which comprisessimultaneously scouring and bleaching the rayon by subjecting it in asingle immersion treatment to the action of an alkaline aqueous solutionhaving a pH maintained within the range of 9' to 12 by means of sodiumsilicate and having dissolved therein hydrogen peroxide in aconcentration within the range of about 0.275 to about 1.65 grams perliter and a synthetic organic water-soluble detergent salt having nofree nor combined carboxyl group, which detergent salt is active in thepresence of the alkali and is resistant to decomposition and oxidationby the hydrogen peroxide.

5. In the treatment of rayon containing color bodies and starchysubstances, the improvement which comprises simultaneously scouring andbleaching the rayon by subjecting it in a single immersion treatment tothe action of an alkaline aqueous solution having dissolved thereinhydrogen peroxide in a concentration within the range of about 0.275 toabout 1.65 grams per liter and sodium lauryl sulfate.

6. In the treatment of rayon containing color bodies and starchysubstances, the improvement which comprises simultaneously scouring andbleaching the rayon by subjecting it in a single immersion treatment tothe action of an alkaline aqueous solution having dissolved thereinhydro- Qibiiltiii I? soon gen peroxide in a concentration Within therange of about 0.275 to about 1.65 grams per liter and sodium laurylsulfate in a concentration approximating /2 gram per liter.

7. In the treatment of rayon containing color bodies and starchysubstances, the improvement which comprises simultaneously scouring andbleaching the rayon by subjecting it in a single immersion treatment tothe action of an alkaline aqueous solution having a pH maintained withinthe range of 9 to 12 by means of sodium silicate and having dissolvedtherein hydrogen peroxide in a concentration Within the range of about0.275 to about 1.65 grams per liter, and sodium lauryl sulfate in aconcentration approximating /2 gram per liter.

8. In the treatment of rayon containing color bodies and starchysubstances, the improvement which comprises simultaneously scouring andbleaching the rayon by subjecting it in a single immersion treatment tothe action of an alkaline aqueous solution having dissolved thereinhydrogen peroxide in a concentration within the range of about 0.275 toabout 1.65 grams per liter and sodium oleyl sulfate.

ARCHIE LOUIS DUBEAU. JAMES DOUGLAS MACMAHON. GEORGE PAUL VINCENT.

